1. Field of the Invention
The present invention relates to feed additives for ruminants. More specifically, the present invention relates to a feed additive composition comprising a biologically active substance that is coated with a coating composition which is stable in the rumen of the ruminant and released in the abomasum or subsequent digestive tract. This ability makes it possible for the biologically active substance to be digested in the abomasum and subsequent digestive tract.
2. Description of the Background Art
In ruminant animals, such as cattle or sheep, the direct oral administration of biologically active substances, such asamino acids and vitamins, causes most of the substances to be decomposed by microorganisms in the rumen; thus they are not effectively utilized.
Accordingly, it is important to pass the biologically active substances through the rumen without decomposition by microorganisms to allow the biologically active substances to be effectively digested and absorbed in the abomasum and subsequent digestive tract. Such an ability would make an impact in the fields of feeds, nutrient preparations and veterinary drugs for ruminant animals.
It was proposed in the past to coat ruminant animal feed additives containing biologically active substances with protective substances, such as fatty acids, hardened animal oils and hardened vegetable oils. However, particles coated with these fats and oils are stable, not only in the rumen, but also in the abomasum and subsequent digestive tract making the biologically active substances difficult to be released in the abomasum and subsequent digestive tract.
For this reason, methods were proposed that added substances propelling the release of the biologically active substances in the abomasum and its subsequent digestive tract that contained such protective substances. In these methods, the biologically active substances are granulated and dispersed in coating materials or coated with coating materials.
The Japanese Laid-Open Patent Publication No. 168351/85 proposes a method of dispersing a biologically active substance in a protective substance which comprises granulating a biologically active substance containing at least 20% by weight of calcium carbonate and at least 10% by weight of a substance selected from the group consisting of monocarboxylic acid, a hardened oil and fat. Furthermore, Japanese Laid-Open Patent Publication No. 195653/86 proposes a process for dispersing a biologically active substance in coating materials composed of at least 10% by weight of a substance selected from the group consisting of a monocarboxylic acid, a hardened oil and fat, and at least 20% by weight to not more than 50% by weight of an insoluble salt of an acid which is more weakly acidic than hydrochloric acid.
As the method of coating with coating materials, for example, Japanese Laid-Open Patent Publication No. 317053/88 describes a method which comprises coating a biologically active substance with a coating material containing the protective substance composed of a monocarboxylic acid, hardened oil, lecithin, and a glycerin fatty acid ester.
However, the method of dispersing a biologically active substance in a coating materials requires that the content of the biologically active substance be considerably decreased in order to retain the protectiveness because the substance is present near the surface of the particle. In view of the fact that the time of passing from rumen to abomasum is between 10 hours to several days, it is difficult to keep the biologically active substances that are present near the surface stable as it passes through the rumen. Furthermore, when the substance is coated with a coating material composed of lecithin, a glycerin fatty acid ester and an oil or a fat, the coated layer has insufficient strength and its protectiveness is diminished. In addition, lecithin and a glycerin fatty acid ester are expected to have an emulsification action of the oil and fat in the small intestine, but because of the length of time required to pass through the small intestine, the property to release the biologically active substances is still not sufficient.
Another method proposed utilizes the difference in pH between the rumen and the abomasum by coating with a polymer which is insoluble in the environment of the rumen but is soluble in the strongly acidic abomasum. Since an organic solvent used for both the coating and the coating agent becomes expensive, this procedure is not a fully satisfactory means.
In view of the foregoing problems, the need exists to provide a method that protects a biologically active substance stably in the rumen of a ruminant animal and yet allows efficient digestion and absorption in the abomasum and subsequent digestive tract.
The present invention provides for such a biologically active substance that can effectively be digested and absorbed by ruminant animals and be safe and economical. Thus, the above objectives have been achieved.